Antirusts



'P atente st. 23?, 1945 White and Roger W. Watson, Ohicago, 111.,assignors to Standard Oil Company, (Ibicago, 1111.,

a corporation of Indiana 'No Drawing. Application November 8, 1943,Serial No. 509,470

14 Claims.

This invention relates to novel compositions of matter having antirustor anti-corrosion properties and to methods for preventing thedevelopment of rust or corrosion in metals.

A wide variety of metals undergo more or less severe corrosion when theyare exposed for a prolonged period of time to the action of water,aqueous fluids, steam, air, exhaust gases produced by internalcombustion engines or other corrosive agencies.

Corrosion is especially prevalent and severe in ferrous metals, such asiron and non-stainless steels used as structural materials in oilcirculation systems wherein purposive mixing or inadvertentcontamination of the oil with water and/or steam occurs. Oil circulationsystems answering the description given above include steam turbine oilcirculation systems, especially in turbines operated at high temperaturewith high pressure steam, and cooling systems wherein a stream of ahydrocarbon oil is recirculated continuously as a thermophoric mediumand wherein water or steam contamination may be prevalent at one or morepoints in the circuit.

Oils desirable for use in systems wherein contamination by water occurs,e. g. in the lubrication of steam turbine bearings and gears, must becapable of demulsifying entrained water rapidly. One of the standardmethods for measuring the emulsifying tendency of oils under serviceconditions is the Herschel demulsibility test, described in the Bureauof Standards Technologic Paper No. 86 (1917). Water entrained oremulsified in oil reduces its lubricating quality with the consequencethat the parts to be lubricated run hotter. Furthermore, the emulsion ofwater in oil iscorrosive to a variety of metals, including the ferrousmetals, and the severity of corrosion increases with increasingtemperature. Another consequence of the increased temperature is theincreased tendency of the oil to oxidize and form organic acids which,with the water present, corrode the metals exposed thereto, with theresulting production of metal soaps of the organic acids. In turn, thesoaps increase the capacity of the oil to emulsify water and air, whichmakes for an increased rate of corrosion. Furthermore, corrosion tendsto produce metallic oxide grits which score bearing surfaces, andasphaltic oil oxidation products which are soluble in the circulatingoil stream at high temperatures but which are not appreciably soluble atlow temperatures so that they settle out in the cool parts of the oilcircuit, resulting in the fouling and plugglng of strainers, tubing andheat exchangers through which the oil stream passes.

It is an object of this invention to provide novel compositionscontaining an amidoxime. Another object of this invention is tobeneficiate various materials by incorporating a small proportion of anamidoxime therein.

An additional object of the present invention is to provide a method ofpreventing or inhibiting corrosion or rusting of metals by theapplication thereto of a novel type of antirust agent. Still anotherobject of this invention is to provide novel oil compositions which willeffectively inhibit the rusting or corrosion of metal surfaces,especially by water or steam.

A further object of this invention is to provide novel oil compositionsadapted to provide prolonged lubrication of metal surfaces exposed towater or steam, while at the same time preventing corrosion of the metalsurface being lubricated. These and other objects of our invention willbecome apparent as the description of our invention proceeds.

Briefly, we have found that metal rusting or corrosion, especially offerrous metals, such as iron and various steels, can be prevented orinhibited by applying to the metal surface to be protected a novel typeof antirust agent. Our invention is especially applicable to thetreatment of metals normally in contact with oils,

but which rust due to partial displacement of the oil film from themetal surface by steam, water or corrosive aqueous solutions.

We have discovered that amidoximes, sometimes called oxamidines orhydroxyamidines, are effective antirust agents for metals normallysubject to corrosion, especially for ferrous metals. The amidoximes area class of organic compounds having the general formula N-OH R-L-NH:which is tautomeric with the formula H-N-OH R- =NH In the above generalformulas, R can be: hydrogen, or an organic radical, such as Alkylgroup: for example, C4H9, CsH1s, CsH17, C11H23-, C13H27, C15H31--,C17Hs5-, etc.,

Alkenyl group: for example, allyl, methallyl, or

oleyl,

Naphthenic or cycloparafiinic: cyclohexyl, methylcyclopentyl, mixturesof naphthenic groups such as are obtainable from petroleum,

Cyclo-olefinic: cyclohexene, methyl cyclohexenes and the like,

Aralkyl: benzyl, naphthomethyl, diphenylmethyl;

An aromatic radical, such as phenyl, naphthyl,

diphenyl, etc. and alkylated aryl groups;

Heterocyclic: thiophene, thiophane, furan,

tetrahydrofurane, pyridine, picolines, piperidine, pyrrol, pyrrolidine,quinoline, quinaldine. etc.

The R group given in the above formulas may contain as substituents avariety of radicals, e. g. halogen, hydroxyl, alkoxyl, aryloxyl,sulfonic, sulfonamide or other sulfur-bearing radicals; nitro, amino,imino, phosphorus containing radicals, etc. We can likewise use amineand ammonia salts of the amidoximes for the purposes of our invention.However, we prefer to use unsubstituted amidoximes.

It is not intended to imply that all amidoximes serve with identicalefilciency as antirust or anticorrosion agents. They will exhibit somevariation depending on the nature and severity of the service to whichthey are subjected, the nature of the metal to be inhibited, therelative solubility of the particular amidoxime in the liquid mediumwhich may be used for application of them to the metal surface to beprotected, and the relative stability of the amidoxime at the servicetemperature.

A number of methods is available for the preparation of amidoximes,including:

(1) The reaction between a nitrile and hi;- droxylamine thehydroxylamine may be added to the reaction mixture as a salt andliberated for reaction by the additionof a base to the reaction mixture;

(2) The reaction between a thioamide and hydroxylamine n IYFOHRQ-NH2+NHIOH=R-NHI+HIS (3) 'Ihereaction between an amidine andhydroxylamine The methods given above for the preparation of amidoximesare merely illustrative and form no part of the present invention.

In accordance with our invention, amidoximes can be used in smallproportions as antirust or anti-corrosion agents for metals,particularly ferrous metals, in a wide variety of media. Thus, theamidoximes may be added in small proportions, for example, in the rangeof about 0.001 to about 0.5% by weight, to-

Motor fuels: for example, automobile or aviation gasolines, tractorfuels, Diesel engine fuels, alcohol-containing motor fuels;

Lighting and heating fuels: kerosene, stove oils, stove and lightingnaphthas, furnace oils, fuel 0 S;

Solvent naphthas: cleaner naphthas, such as Stoddard solvent, V. M. andP.- naphthas, hydroformed naphthas;

Lubricating and dielectric oils: motor 0115, Diesel oils, aviationengine oils, marine engine lubricants, gear oils, oil field machinerylubricants, ice-machine oils, steam cylinder lubricants, transmissionoils. soluble oils, textile oils, cutting oils, turbine oils, insulatingoils;

Lubricating greases: stable gel-like or. solid dispersions of metalsoaps in hydrocarbon oils;

Protective coatings: slushing oils and greases in which part or all ofthe hydrocarbon oil may be replaced by metal soaps and/or waxes such asthe ester-type waxes, mineral waxes such as petrolatum and paraffinwaxes, pitches, tars. asphalt, rosin asemas The amidoximes are useful inpreventing rusting of metal parts which are brought into contact withthe above oils, waxes, etc., in the presence of water, air, steam orother normally corrosive influences. Thus, in the stora'geofhydrocarbons a water seal is often used in the bottom of the storagetank. In addition the refining of hydrocarbon oils generally results inthe intrusion of small proportions of water. Also, the storage and useof hydrocarbon oils generally results in more or less extensivecontamination thereof with water. The amidoximes prevent rusting orcorrosion of metals, especially ferrous metals, in hydrocarbon oilstorage tanks, pipe lines, preheaters, etc.

Amidoximes may also be used as rust inhibitors and for other purposes invegetable, animal and marine oils; in proportions varying from about0.005% by weight to about 1% by weight or even more. Also, amidoximescan be added in small proportions to blends of the above t p s of oilswith hydrocarbon oils.

The amidoximes may also be used as metal corrosion inhibitors in othermedia. For example, soluble amidoximes may be used as corrosioninhibitors in engine coolant liquids such as water, aqueous alcohols,slycols and the like.

A preferred class of applications of amidoximes as rusting inhibitors isin viscous highly refined hydrocarbon oils, such as steam turbine oilswhich are applied in services wherein contamination of the oil withwater or steam induces rusting or metal parts, especially ferrous metalparts, encountered by the oil. Steam turbine oils generally have SayboltUniversal viscosities at 100 F. of from about 125 seconds to about 2000seconds or even higher.

The capacity of turbine oils to form quickbreaking emulsions with wateris essential to successful operation; therefore, no addition agent whichwill result in appreciable reduction of the demulsibility of the oil canbe tolerated. In general, from about 0.001 to about 0.5% by weight of anamidoxime is sufllcient to confer adequate rust inhibition to viscoushighly refined hydrocarbon oils without sensibly affecting theiremulsifying properties.

The following illustrative examples relate to the application ofamidoximes as antirust agents in turbine oils. The rustingcharacteristics of turbine oils containing these additives isdemonstrated by the following test: 300 ml. of the oil to be tested areplaced in a 400 ml. lipless glass beaker heated to about 167 F. in anoil bath and the oil is stirred by means of a stirrer maintained atabout '150 R. P. M. When the temperature of the oil sample reaches about167 F., a polished test strip of cold-rolled steel is suspended in theoil and stirring continued for 30 minutes to insure complete wetting ofthe steel specimen. Thirty ml, of distilled water are then carefullyadded by pouring down the side of the beaker, and stirring is continuedfor 24 hours. At the end of this time the steel specimen is removed fromthe beaker, washed with naphtha and inspected visually for the presenceof rust. The method of carrying out this test has been described inNational Petroleum News, Section 2, Volume 34, No. 30 (July 29, 1942)page R-216, except that the test temperature therein recommended isabout F. instead of 167 F. and the duration of the test is 48 hoursinstead of 24 hours as in our tests.

The test pieces are rated numerically 1 to 5 according to increasingamounts of corrosion. A

rating of l is given to test pieces showing no rust or discoloration; arating of is given to'severely rusted pieces resulting from tests onuninhibited oils.

In the following examples the control is a technical white oil having aviscosity of 145 seconds Saybolt Universal at 100 F. produced bytreating a lubricating oil distillate with about 6 lbs. of

104.5% sulfuric acid per gallon of distillate, and normally used forsteam turbine gear and bearing lubrication. All percentages are byweight based on the total composition.

In Example 4, above, the naphthenamidoximes were prepared fromcommercial mixed petroleum naphthenic acid.

Napthentic acids are complex mixtures of carboxylic acids which occurnaturally in various crude petroleum oils, usually in proportions below1 per cent, and may be extracted therefrom by the use of alkalies.Extensive research has demonstrated that petroleum naphthenic acids fallinto at least three general categories; (1) allphatic acids having thegeneral formula CnHZnOB and predominating in compounds wherein 11. is 6or 7, (2) acids having the general formula CnHEn-QOB and shown to becyclopentane derivatives C5H9' (CH2)=CO2H, where a: generally variesfrom 1 to about 4 and wherein the cyclo pentane ring may also containone or more alkyl groups, (3) acids having the general formula cnH2n402,known to contain a bicyclic cycloaliphatic nucleus and containing about12 to about 25 carbon atoms. The above classification presents asomewhat over-simplified picture. Some evidence has been adduced of theexistence of even more complex acids in petroleum naphthenic acids,including triand tetra-cyclic cycloaliphatic-substituted aliphaticcarboxylic acids.-

There is evidence that the molecular weights in the above classesoverlap; thus, although the simple aliphatic acids predominate in Co orC1, small proportions of higher molecular weight fatty acids also occurand overlap into the molecular weights and boiling ranges of compoundsfalling into categories (2) and (3) above. Naphthenic acids obtainedfrom different crudes and from various fractions of the same crude oilgenerally differ from each other somewhat in composition and character.

The naphthenamidoximes of Example 4 were prepared by converting thenapthenic acids to the corresponding mixture of amides, dehydrating theamides to produce a mixture of nitriles and reacting the nitriles with asalt of hydroxylamine in the presence of a base.

Example 5 describes the use of an aryloxy alkyl amidoxime as anantitrust agent in a turbine oil.

In the above examples, it was found that the emulsifying characteristicsof the control were substantially unchanged by the addition of theamidoximes, as revealed by the Herschel Demulsibility Test.

Although a wide variety of amidoximes can be used to confer rustpreventive properties upon hydrocarbon oils, we prefer to use a mixtureof naphthenamidoximes, such as are derivable from petroleum naphthenicacids. The naphthenamidoximes appear to confer somewhat improvedprotection, as compared with other amidoximea;

this improvement appears to be due, at least in 1 corrosion. Forexample, the amidoximes may be used in combination with about 10 toabout by weight, based on the amidoxime, of hydroxylamine, hydroxamicacids, preferably naphthenhydroxamic acids, alkylamine salts of organicacids, e. g. amylamine salts of mahogany acids and the like.

The oils in which the amidoximes are usedmay, in addition, contain V. I.improvers, viscosity-increasing agents, bloom-producing agents, extremepressure agents, antioxidants, dyes, and antiknock agents, as the casemay be, provided only that these additional agents do not enter intoappreciable chemical reaction with the amidoximes or precipitate themfrom the oils towhich they have been added.

Thus in turbine oils, we can, in addition to an amidoxime, add anantioxidant such as the polyhydric phenols and their alkyl derivatives,for example catechol, tertiary butyl catechol, octyl catechol. Otherefiective antioxidants include beta-naphthol, amyl beta-naphthol, octylbetanaphthol, lauryl beta-naphthol, alpha-naphthol, amyl alpha-naphthol,N-phenyl alpha-naphthylamine, di-aJpha-naphthylamine and the like. Theantioxidant may suitably be used in a proportion in the range of about0.001 to about 0.25% by weight based on the oil.

We claim:

1. A composition of matter comprising a major proportion of an oil and aminor, corrosion-inhibiting proportion of an amidoxime.

2. A com-position of matter comprising a major proportion of ahydrocarbon oil and a minor, corrosion-inhibiting proportion of anamidoxime.

3. A composition of matter comprising a major proportion of ahydrocarbon oil and a minor, corrosion-inhibiting proportion of anamidoxime having the formula wherein R is an organic radical.

lIF-O R-C-NHa.

wherein R is an alkyl radical.

5. A composition of matter comprising a major proportion of ahydrocarbon oil-and a minor, corrosion-inhibiting proportion of anamidoxime having the formula N-OH R-E-NH, wherein R is an alkyl radicalcontaining an aryloxyl radical as a substituent.

6. A composition of matter comprising a major proportion of ahydrocarbon oil and a minor, corrosion-inhibiting proportion of anamidoxime having the formula 1 x-on B-C-NH:

wherein R is an aromatic radical.

'7. A composition of matter comprising a major proportion of ahydrocarbon oil and a minor, corrosion inhibiting proportion of anamidoxime having the formula Ill-OH n-c-Nm wherein R is a naphthenicradical.

8. A composition of matter comprising a major proportion of ahydrocarbon oil and a. minor, corrosion inhibiting proportion oflauramidoxime.

9. A composition of matter comprising a major proportion of ahydrocarbon oil and a minor,

the presence of water in systems susceptible to corrosion by said water.comprising a major proportion of an oil and a minor. corrosioninhibiting proportion of an amidoxime having the formula ic-on wherein Ris an alkyl radical.

12. A rust inhibiting oil composition for use in the presence of waterin systems containing metal susceptible to corrosion bysaid water,comprising a major proportion 01' an oil and a minor, corrosioninhibiting proportion of an amidoxim having the formula lax-on B-C-NH:wherein R is an aromatic radical.

13. A rust inhibiting oil composition for use in v the presence of waterin systems containing metal susceptible to corrosion by said water,comprising a major proportion of an oil and a minor, corrosioninhibiting proportion of an amidoxime having the formula n-c-mn whereinR is a naphthenic radical.

14.-. A composition of matter comprising a major proportion of 9,non-gaseous hydrocarbon and a minor, corrosion-inhibiting proportion ofan amidoxime.

JAMES w. GAYNORH cLARoN N. WHITE. ROGER w. WATSON.

